Pedal seized, but I don't know why.

alomac

As the title says, I removed the cranks from my MTB for an upgrade, only to find that the left pedal had seized solid on to the crank (and yes, I made sure that I was turning it the right way). I tried penetrating oil, hammering the wrench and so forth, but ultimately I ended up sawing into the crank'sto free them (the cranks were at the end of their life anyway, and all the wrenching was starting to damage the pedals).

It sounds like a straightforward seizure, but... while the pedals had been on the bike for most of the year, I've only been able to ride a handful of times and always in good weather. Furthermore, I thoroughly coated the threads with marine grease when I installed the pedals and sure enough, when I finally got the pedal out, there was still a thick coating of the stuff on threads. The pedal and crank threads appear fine and undamaged, apart from where I chopped the cranks.
I have installed and replaced pedals many times (this MTB is on its third set, my commuter has gone through four sets of pedals and two cranks) and have never had a problem before. Indeed, these pedals should have been the least likely to give problems as they've seen the least service and the best conditions by a long way.

The pedals and cranks are just standard: Cro-Mo-axled Shimano M530s on Alivio (M442) cranks. I'm kind of reluctant to put the pedals on my shiny new Deore cranks until I figure out what happened. Does anyone have any ideas?

nicklouse

i still dont understand why people use grease in a non moving application. use an anti seize next time and get a pedal spanner.

and it just happens.

alomac

I will be using an anti-seize from now on, though as mentioned the pedal didn't seem to seize in the usual sense and grease has always worked fine before.

I do have a pedal spanner, btw. I moved to a fixed-socket wrench once it became clear that the pedal was stuck as the pedal flats are wide enough to accommodate it, the wrench has a greater grip area and it didn't flex the way the (admittedly cheap) pedal spanner did under high loads.

njee20

You say you turned it the 'right way', which way was that?

Balaclavas

I may have misread but it should be a lot easier to remove the pedal before taking the crank off the bike. Gives something to push against.

paul.skibum

Balaclavas wrote:

I may have misread but it should be a lot easier to remove the pedal before taking the crank off the bike. Gives something to push against.

^This and

njee20 wrote:

You say you turned it the 'right way', which way was that?

^This

Oh what the hell and This -

nicklouse wrote:

i still dont understand why people use grease in a non moving application. use an anti seize next time and get a pedal spanner.

and it just happens.

alomac

paul.skibum wrote:

Balaclavas wrote:

I may have misread but it should be a lot easier to remove the pedal before taking the crank off the bike. Gives something to push against.

^This and

Indeed, but I had an appointment to get the BB shell faced, and needed the cranks off. I should have left things till I got the bike back and reinstalled the crank/pedal and started again, but I let impatience and frustration get the better of me.

paul.skibum wrote:

njee20 wrote:

You say you turned it the 'right way', which way was that?

^This

Clockwise. It's a left hand pedal.

paul.skibum wrote:

Oh what the hell and This -

nicklouse wrote:

i still dont understand why people use grease in a non moving application. use an anti seize next time and get a pedal spanner.

Grease is recommended freequently enough. See Park Tool and Sheldon Brown. I already mentioned that I own a pedal spanner.

paul.skibum wrote:

nicklouse wrote:

and it just happens.

There must be a reason.

The Rookie

Usually moisture getting in, it causes oxidation, the oxide is a larger volume than the original metal and jams the threads up.

sectongguo

though as mentioned the pedal didn't seem to seize in the usual sense and grease has always worked fine before.